LEC 2: KNEE

what do the menisci do?

act as shock absorber; keeps tibial plateau away from the femoral condyle

what do the cruciate ligaments do?

prevent anterior and posterior displacement of tibia

what do the collateral ligaments do?

give medial and lateral stability and prevent dislocation

what do the bursa sacs of the knee do?

Protect and cushion the knee joint

what is the synovial fluid in the knee and what does it do?

thick, apricot colored fluid that allows gliding

what happens to synovial fluid if the knee is continually irritated?

it will be hyperproduced & we can aspirate it

what do the femoral condyles do?

stabilize knee joint; face the tibial plateau

what is the tibial plateau?

proximal tibial surface on which the femur rests

what is the patella?

kneecap

what 2 tendons attach to the patella?

quadriceps tendon & patellar tendon

what is important to look at w/ the patella?

its positioning

what is the m/c mechanism of tearing a meniscus?

extensive medial/lateral rotation of the tibia on the femur

how many degrees does the knee flex?

0-135

how many degrees does the knee extend?

0-15

what is so important about the lateral femoral condyle?

it is much more shallow which is a reason why lateral patella dislocation is m/c

what is patella glide?

passive lateral motion of patella should achieve approx 50% subluxation w/ knee in ext

what does the patellar tendon grab on to?

the tibial tubercle

what is important about the proximal fibula (think neuro)?

the peroneal nerve wraps around it

what are the extensors of the knee?

quads- rectus femoris, vastus lateralis, vastus medialis, vastus intermedius

what tends to occur w/ the vastus lateralis?

it tends to form/grow more quickly

what are the flexors of the knee?

hamstrings- biceps femoris, gracilis, semitendinosus, semimembranosus

what is the fascia latra?

envelop that surrounds the muscles of the thigh (can cause compartment syndrome)

where is compartment syndrome m/c?

lower leg (it has 3 compartments)

what causes compartment syndrome?

result of trauma w/ considerable soft tissue damage, fracture, crush injury; can also result from infx

what are the 5 P's of compartment syndrome?

pain, paresthesias, paralysis, pallor, pulselessness, poikilothermia

A 16 year old patient comes in and says that they were playing soccer when they planted their foot, twisted, and heard an audible pop. What is the most likely diagnosis?

ACL tear

what is the ACL composed of?

2 bundles in 1 sheath (intracapsular but extra synovial)

what is the gold standard dx tool for an ACL tear?

MRI

A patient comes into the ER following a MVA where they had their knees hit the dashboard. What is the most likely dx?

PCL tear

what does the MCL prevent?

valgus angulation of the knee

how are the medial & lateral menisci shaped?

medial: C shaped

lateral: circular

what are the functions of the menisci?

deepen the articular surface, shock absorption, add stability, lubricate, nutrition

what does the blood supply do the menisci not include?

the inner portion of the meniscus

what is normally done if the inner portion of the meniscus is injured?

we tend to shave it away when torn

what puts the meniscus under extreme stress?

locking the knees out in extension

what type of meniscal tear is m/c?

medial meniscus b/c the medial femoral condyle is longer & articulates 1st

what is the m/c injury to the knee requiring surgery?

meniscal tear

what type of onset do we see in meniscal tears in older/elderly people?

insidious onset

what type of onset do we see in meniscal tears in younger people?

acute onset

what can cause meniscal tears?

twist or trauma (acute) or degenerative

what is the m/c/c of a locked knee?

meniscal tear (requires urgent intervention)

what is a bucket handle tear?

an incomplete longitudinal tear forming a C-shape; causes clunking & limits motion

what can help w/ a bucket handle tear?

a little traction to get the meniscus to flip back over

what do we see in the history of a patient presenting w/ a meniscal tear?

locking/catching episodes, giving way, pain w/ squatting, Baker's Cyst swelling

what tests are positive w/ a meniscal tear?

+ effusion, + joint line tenderness (from A --> P), + McMurray, + Apley Compression test

what imaging dx a meniscal tear?

MRI

how can we tx meniscal tears?

arthroscopic repair (if in an area w/ blood supply), partial meniscectomy (removal of torn piece)

what is the 1st line tx w/ degenerative meniscal tears?

NONOP- RICE, NSAIDs, PT, cortisone

what is visco supplementation?

injections into the joint space; sodium hyaluronic acid + cartilage

when do meniscal cysts occur?

when something is aggravated

what meniscus is m/c affected by meniscal cysts?

lateral meniscus w/ horizontal cleavage tears; mostly benign

what is popping knee syndrome caused by?

discoid meniscus; congenitally malformed lateral meniscus

what are the s/sx of discoid meniscus?

knee instability & popping w/ knee extension usu in early childhood during growing or during athletic mvmts

what causes an MCL sprain?

valgus force

how is an MCL sprain dx?

+ tenderness along MCL, + opening of medial joint line w/ valgus stress when knee @ 30º of flexion

what is a grade I MCL sprain?

tenderness w/o laxity

what is a grade II-III MCL sprain?

tenderness & extreme laxity

what is the tx of MCL sprain?

RICE, NSAIDs, PT, bracing, or surgery

most people will get to the same point w/in a year if they get surgery or not

what causes an LCL sprain?

varus force to the knee (uncommon)

how do we dx LCL sprain?

+ tender along LCL, + opening of lateral joint space w/ varus stress when knee @ 30º flexion

what do we normally see w/ an ACL tear?

hemarthosis!

IF serosanguinous- think bone frx & give abx

how is an ACL tear dx?

+ lachman, + anterior draw, + pivot shift w/anterolateral instability, hemarthosis on arthrocentesis

what is the m/c initial test in the field for ACL tears?

lachman

what is the gold standard imaging for an ACL tear?

MRI

what do we give pt's post ACL surgery?

post op CPM (continuous passive motion machine), hinged knee brace, progressive PT

what is the unhappy triad?

MCL tear, Medial Meniscal Tear, ACL rupture (seen w/ athletic injury via trauma)

how is the unhappy triad tx?

ACL needs to get fixed!, normally surgery is staged; knee immobilization for 2 weeks, then begin PT for ROM

how do we dx PCL tears?

+ posterior draw, + sag sign (when leg outstretched & tibia is depressed)

what are we concerned w/ in a PCL tear?

popliteal artery injury; ALWAYS ASSESS DISTAL PULSES

what is patella tendonitis?

jumpers knee seen in basketball/volleyball players

how is patella tendonitis dx?

+ tenderness along patella tendon

how is patella tendonitis tx?

RICE, NSAIDs, limit activity, PT

what are the signs of a patella tendon rupture?

palpable/visible defect in patella tendon, cannot actively extend knee

what does xray show w/ a patella tendon rupture?

patella alta or high riding patella

how do we tx a patella tendon rupture?

NEEDS SURGERY; WB as tolerated w/ locked knee extension x6 weeks, then progressive ROM PT

what is the c/o pain in PFPS (chondromalacia)?

pain going up or down stairs

what does exam show in pt's w/ chondromalacia?

inc Q angle, + patella grind, + patella apprehension tests

what type of xray do we get and what does it show in chondromalacia?

xray w/ sunrise view; shows lateral tilt of patella (jammed over to one side)

how do we tx chondromalacia?

PT for quad strengthening, NSAIDs, Ice, knee sleeve (J brace)

who is IT band friction syndrome common in?

runners & cyclists

what causes ITB syndrome?

friction b/w ITB & lateral femoral condyle

what do we see on physical exam of ITB syndrome?

+ tenderness over lateral epicondyle @ 30º flexion, may be tender throughout, tends to migrate proximally if left untx

what is the tx of ITB syndrome?

limit activity, ice, PT, NSAIDs, +/- cortisone

what do we suspect if pt is tx for a meniscal tear w/ cortisone injections, but now the pain has migrated to the lateral thigh?

it's not a meniscal tear, it's ITB syndrome!

what way does a patella usually subluxate?

laterally

how is a patella subluxation reduced?

w/ knee extension

what do we see on physical exam of patella subluxation?

+ patella apprehension test, visual deformity w/ dislocation

how do we tx patella subluxation?

tx like chondromalacia

what do we do if instability persists w/ patella subluxation?

lateral release w/ medial stabilization

what causes a patella fracture?

result of direct blow or fall

what should we do 1st if we suspect a patella fracture?

get xray & check distal pulses

what do we see on exam of a patella fracture?

+ patella apprehension, + patella femoral grind, probable edema

how do we tx patella fracture?

casting, possibly surgery (k wires, cannulated screws, circumferential wire cerclage)

what knee bursa is m/c affected by bursitis?

pre patella bursa

what is the m/c misdiagnosed/missed bursitis?

pes anserine

what causes bursitis?

irritation & trauma

how do we tx bursitis?

aspirate, leave needle in & inject steroids to scar the bursa sack so bursitis doesn't recur

what do we do if a pt has septic bursitis?

must send aspirate for culture & consider IV abx or PO abx vs I&D

what do we see w/ synovitis of the knee?

aspiration is thick & murky (mimics infected fluid BUT it's NOT infected)

what can synovitis lead to?

a baker's cyst (in posterior popliteal fossa)